The invention relates to a switching device for optionally passing a flow of medium, for example a highly pressurized gas, through a first or second treatment member, in which the said medium is subjected to a treatment, such as filtration, heating, cooling or the like, comprising:
a medium inlet, a medium outlet and two distribution valves, of which the valve bodies, which are provided with passages, are attached to a common rotation pin, all this in such a manner that, in one limit position of the said rotation pin, the inlet and the outlet of the switching device are connected to the first treatment member, and in the other limit position of the said rotation pin, the inlet and the outlet of the switching device are connected to the second treatment member, and
safety valves arranged in the connections between the distribution valves and the two treatment members.
A switching device of this type is known from GB-A-2236829.
A switching device as indicated in the preamble can be used, for example to pass natural gas which is at a high pressure (for example 200 bar) through one of the two filters alternately. While the one filter is in use, the other filter is replaced and/or purged with, for example, nitrogen. If a distribution valve, usually a ball valve, leaks, gas enters the filter which at that time is being cleaned by purging or replaced. This may be very dangerous. Therefore safety valves are arranged in the connections between the distribution valves and the two treatment members.
If a distribution valve leaks in the direction of a treatment member which is not in operation, leakage gas is blocked by a safety valve.
According to the invention two safety valves in the connections between the distribution valves connected to the inlet and outlet and the first treatment member are arranged on a common rotation pin and the valve bodies of the two safety valves in the connections between the distribution valves connected to the inlet and outlet and the second treatment member are likewise arranged on a common rotation pin.
It is important that the valves be switched correctly during the transfer from one treatment member to the other. For this purpose, a pressure-equalization line having at least one shut-off member extends between the two treatment members and a switching system for switching the distribution valves and safety valves is added to the device, acting in such a manner that, to switch over the supply and discharge of medium to and from one treatment member to and from the other treatment member, the following switching operations take place in succession:
the valve bodies of the safety valves in the supply and discharge lines of the treatment member which is not operating are moved into the open position, in which the valve bodies of the safety valves in the supply and discharge lines of the operating treatment member are blocked against rotation,
the at least one shut-off member in the pressure-equalization line is opened,
the valve bodies of the distribution valves are moved into a position in which the treatment member which was not previously operating is activated, and the operating treatment member is deactivated, the treatment member which has just been activated being blocked against rotation,
the at least one shut-off member in the pressure-equalization line is closed, and the valve bodies of the safety valves in the inlet and outlet of the treatment member which has just been deactivated are moved into the closed position.
In this way, the valves of the system could be switched electronically. However, it is safer if the switching system contains the following parts:
a circular disc which is arranged on the common axis of the distribution valves and has two cutouts, which are in the form of segments of a circle and follow one another over the circumference thereof,
a circular disc which is arranged on the common axes of each of the safety valves and has one cutout in the form of a segment of a circle on the circumference, the radius of the circle-segment cutouts being equal to that of the circular discs, and imaginary circles around the circumferences of the discs which are arranged next to one another overlapping one another over the shape and size of one circle-segment cutout.